Last Updated: 2017-06-29 02:14:53 UTC
by Brad Duncan (Version: 1)
"Blank Slate" is the nickname for a malicious spam (malspam) campaign pushing ransomware targeting Windows hosts. I've already discussed this campaign in a previous diary back in March 2017. It has consistently sent out malspam since then. Today I collected 11 Blank Slate emails, so this diary examines recent developments from the Blank Slate campaign.
Today's Blank Slate malspam was pushing Cerber and GlobeImposter ransomware.
Normally, emails from this campaign are blank messages with vague subject lines and attachments that don't indicate what it is. That's why I've been calling it the "Blank Slate" campaign.
However, since yesterday, the Blank Slate campaign has sent several Microsoft-themed messages. We've seen this before. As recently as 2017-04-13, I documented Blank Slate malspam using fake Microsoft messages that led to fake Chrome installation pages. Those fake Chrome pages sent victims zip archives containing malicious .js files designed to infect Windows hosts with ransomware.
Today's messages look similar to previous Microsoft-themed emails; however, this time they don't have links to a fake Chrome page. Instead, they have zip attachments containing malicious .js files.
Otherwise, these emails are similar to previous waves of Blank Slate malspam.
As usual, the zip attachments are double-zipped, and they contain a .js file designed to infect a Windows computer with ransomware. I saw two types of .js files. One was about 9 kB in size, and it ran the downloaded ransomware from the user's AppData\Local\Temp directory. The other type of .js file was about 31 kB in size, and it ran the downloaded ransomware from the user's AppData\Roaming\Microsoft\Windows\Templates directory.
Traffic is also typical of what we've seen before with Blank Slate malspam. Ransomware binaries are typically downloaded in the clear from a domain name ending with .top.
No post-infection traffic was noted for today's GlobeImposter ransomware. I saw the typical post-infection for today's Cerber samples.
As others have noted Twitter and elsewhere, recent Cerber samples use "CRBR" as their name in the decryption instructions. File extensions used by Cerber for any encrypted files consist of 4 characters based on the MachineGuid of the infected Windows host.
GlobeImposter also acts the same as we've seen before. Encrypted files use the .crypt file extension.
Indicators of Compromise (IOCs)
The following are SHA256 hashes for the today's extracted .js files:
- 10358fb055b8d8e0d486eafc66be180d52481667fb63bf4e37bf9cafe5a0dbdb - 7941.js
- 153b11ae2df30b671bd0bd54af55f83fd2a69e47c8bb924b842bc1b44be65859 - 25601.js
- 1cbf043831b16ca83eeaff24f70b1a3ea4973d2609e64db33fd82cc0629f1976 - 6935.js
- 567bb9c835306e02dbedc5f10e32c77a2c6f1c2f28ff49c753f963776a9378b5 - 30085.js
- 7ecd1253aad0935df1249d6504d3f4090a00466fa159c2ec4e2d141b4b75068f - 9177.js
- 8b7202a672290e651f9d3c175daaf2b8a3635eba193e925da41bd880a611f2af - 13521.js
- 8ec6455eb9f8a72fef35e9a330e59153f76b8ebd848c340024669e52589ceb18 - 23288.js
- b6ab00337d1e40f894ca3959ee9a19e4c9e59605ed1f2563f0bde4df5f76981b - 27465.js
- c9f71912dd39d4d4ed9f54f6a51f99ee0687e084c2e8782f0b0d729b743e7281 - 3047.js
- d19233fd99213f5a1d299662d9693eb6bc108d72ce676893bc69c8d309caa54a - 26715.js
- ed855d0b4cfd5150a4b44a1d3b6c26224e2990743d977804bab926d569aa963b - 24703.js
The following are SHA256 hashes for ransomware samples downloaded by the extracted .js files:
- 0dc831b502f29d4a6a68da9e511feb8c646af4fcfdeaaee301cb5b0dbaf47c5f - Cerber
- 703b1ea2b0310efdc194b178c777c2e63d5ad1b7f2ac629c01ffa1b36859ba2f - GlobeImposter
- b1be5af4169014508b17d2de5aa581ea62988cc4d3570ed2ed7f9fb931a5902b - Cerber
- d1ed3742380539fbef51804e1335c87dd0ef24a6de7f0aa09ce26ad1efe4bcef - Cerber
The following are domains, HTTP requests, and IP addresses associated with today's Blank Slate malspam:
- 18.104.22.168 port 80 - coolfamerl.top - GET /1 [returned Cerber]
- 22.214.171.124 port 80 - clippodoops.top - GET /403 [returned GlobeImposter]
- 126.96.36.199 port 80 - clippodoops.top - GET /1 [returned Cerber]
- 188.8.131.52 thru 184.108.40.206 (220.127.116.11/27) UDP port 6893 [Cerber post-infection scan]
- 18.104.22.168 thru 22.214.171.124 (126.96.36.199/27) UDP port 6893 [Cerber post-infection scan]
- 188.8.131.52 thru 184.108.40.206 (220.127.116.11/22) UDP port 6893 [Cerber post-infection scan]
- 18.104.22.168 port 80 - xpcx6erilkjced3j.1t2jhk.top - Domain leading to the Cerber decryptor
Email from the GlobeImposter decryption instructions: firstname.lastname@example.org
As I noted last time, potential victims must open the zip attachment, open the enclosed zip archive, then double-click the final .js file. That works on default Windows configurations, but properly-administered Windows hosts and decent email filtering are enough, I think, to keep most people from worrying about Blank Slate.
This is definitely not as serious the recent Petya/NotPetya ransomware outbreak on 2017-06-27. I still wonder how many people are fooled by Blank Slate malspam. Does anyone know someone who was actually infected from these emails? If so, please share your story in the comments section below.
Pcap and malware samples for this ISC diary can be found here.
brad [at] malware-traffic-analysis.net
Last Updated: 2017-06-28 17:10:43 UTC
by Brad Duncan (Version: 1)
This is a follow-up the our previous diary on the ransomware outbreak that happened yesterday on Tuesday 2017-06-27.
By now, it seems almost everyone has written something about yesterday's ransomware outbreak. This led to some confusion after more information became available, and initial reports were updated. This diary acts as a summary of what we know so far.
What we know so far
This ransomware targets systems running Microsoft Windows. Although initial reporting called this ransomware Petya or a Petya variant, Kaspersky researchers reported it's a new ransomware. Kaspersky has been calling the malware NotPetya, and other names have been floating around for it. However, many people and organizations still call the ransomware Petya or a Petya variant.
This ransomware uses a modified version of the EternalBlue SMB exploit, and it also spreads using other methods like WMI commands, MimiKatz, and PSExec. Although exploits for EternalBlue are relatively recent, malware has been using file shares and WMI to spread for years, and these older techniques don't require any vulnerabilities.
During the infection process, this ransomware overwrites the MBR with a custom boot loader that implements a tiny malicious kernel. That tiny kernel encrypts the master file table (MFT) so the file system is unreadable. The result is an unbootable system that demands a ransom to restore it. The victim is asked to send $300 USD in Bitcoin to a Bitcoin wallet at 1Mz7153HMuxXTuR2R1t78mGSdzaAtNbBWX.
Based on public reports, this attack appears to have originated in Ukraine. According to Krebs on Security the Ukrainian Cyber Police tweeted this attack may have started through a software update mechanism built into M.E.Doc, an accounting program used by companies working with the Ukrainian government. From the Ukraine, it spread to major European firms like Maersk.
Although we've seen some information on files related to this ransomware, we can only confirm two DLL files as samples of the actual ransomware. The SHA256 file hashes are:
How can you protect yourself against this threat? Steps include:
- Deploy the latest Microsoft patches, especially MS17-010.
- Consider disabling SMBv1.
- Restrict who has local administrative access. Most people can operate with Standard User accounts instead of Administrator accounts.
- If you have a large or complex infrastructure, segment your network.
- Keep your anti-virus software up-to-date. Vendors are constantly updating definitions to cover the latest malware samples.
Most importantly, you should implement a solid backup and recovery procedure for your critical data, just in case the worst happens and you get infected.
The day after this ransomware attack, our initial excitement has died down a bit. Affected organizations are conducting response actions, and many others are implementing (or confirming) proper countermeasures.
We hope your organization is following best security practices and is protected against this latest threat.
brad [at] malware-traffic-analysis.net